Balloon catheter with improved pushability

ABSTRACT

Rapid exchange angioplasty catheters and methods of constructing rapid exchange angioplasty catheters including features that provide good pushability and kink resistance. In an illustrative embodiment, a catheter is provided, the illustrative catheter including a proximal hypotube section, which connects to a more distal braided catheter section. The braided catheter section connects to a midshaft portion that includes a guidewire entry port. Distal of the midshaft portion is a distal section having a balloon disposed thereon. An inflation lumen extends the length of the catheter, while a guidewire lumen extends only from the guidewire entry port to the distal end of the catheter. Optionally, a core wire may extend across the joint from the hypotube, to the braided catheter section, and past the guidewire entry port.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/464,407, filed May 4, 2012, which is a continuation of U.S.application Ser. No. 12/638,318 filed Dec. 15, 2009, now U.S. Pat. No.8,172,864, which is a continuation of U.S. application Ser. No.10/436,216, filed May 12, 2003, now U.S. Pat. No. 7,632,288, the entiredisclosures of which are incorporated herein in their entirety.

FIELD OF THE INVENTION

The present invention pertains to angioplasty and angioplasty ballooncatheters. More particularly, the present invention pertains toangioplasty cutting balloon catheters that include improved pushability

BACKGROUND OF THE INVENTION

Heart and vascular disease are major problems in the United States andthroughout the world. Conditions such as atherosclerosis result in bloodvessels becoming blocked or narrowed. This blockage can result in lackof oxygenation of the heart, which has significant consequences sincethe heart muscle must be well oxygenated in order to maintain its bloodpumping action.

Occluded, stenotic, or narrowed blood vessels may be treated with anumber of relatively non-invasive medical procedures includingpercutaneous transluminal angioplasty (PTA), percutaneous transluminalcoronary angioplasty (PTCA), and atherectomy. Angioplasty techniquestypically involve the use of a balloon catheter. The balloon catheter isadvanced over a guidewire so that the balloon is positioned adjacent astenotic lesion. The balloon is then inflated, and the restriction ofthe vessel is opened. It is typically considered desirable to have acatheter which varies in flexibility along its length, from a stifferproximal section to a more flexible distal section.

One of the major obstacles in treating coronary artery disease and/ortreating blocked blood vessels is restenosis. Evidence has shown thatcutting the stenosis, for example with an angioplasty balloon equippedwith a cutting blade, during treatment can reduce incidence ofre-stenosis in certain applications. Additionally, cutting the stenosismay reduce trauma at the treatment site and/or may reduce the trauma toadjacent healthy tissue. Cutting blades may also be beneficial additionsto angioplasty procedures when the targeted occlusion is hardened orcalcified. Thus, angioplasty balloons equipped with cutting edges havebeen developed to attempt to enhance angioplasty treatments.

SUMMARY OF THE INVENTION

The present invention includes catheters adapted for use as rapidexchange angioplasty catheters including features which provide goodpushability and kink resistance. In a first embodiment, a rapid exchangecutting balloon angioplasty catheter is provided, the illustrativecatheter including a proximal hypotube section which connects to a moredistal braided catheter section. The braided catheter section connectsto a midshaft portion that includes a guidewire entry port. Each of thehypotube, braided catheter section, and midshaft portion includes atleast one inflation lumen for providing fluid communication from aproximal end of the catheter to a distally disposed cutting balloon.Distal of the midshaft portion is a distal section having an inflationlumen and a guidewire lumen, and a cutting balloon is disposed on thedistal section in fluid communication with the inflation lumen. In afurther illustrative embodiment, a core wire extends across the jointfrom the hypotube to the braided catheter section and may even extendpast the guidewire entry port. The use of a braided catheter sectionjust distal of the hypotube not only allows for a kink-resistanttransition but also provides additional pushability for that portion ofthe shaft, while still adding to the flexibility and softness of thecatheter shaft distal of the hypotube.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a balloon angioplasty catheter;

FIG. 2 is a cross-sectional side view of an illustrative guidewire entryport;

FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. 2;

FIG. 4 is a cross-sectional side view of an illustrative cuttingballoon;

FIG. 5 is a cross-sectional view taken along line 5-5 in FIG. 4;

FIG. 6 is a cross-sectional view taken along line 6-6 in FIG. 4;

FIG. 7 is a top view of an illustrative slit and flared member;

FIG. 8 is a side view showing a step of forming an illustrative portjoint;

FIG. 8A is a cross-sectional view taken along line A-A in FIG. 8;

FIG. 9 is a side view showing another step in forming an illustrativeport joint;

FIG. 10 is a side view showing yet another step in forming anillustrative port joint; and

FIG. 10A is a cross-sectional view taken along line A-A in FIG. 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description should be read with reference to the drawingswherein like reference numerals indicate like elements throughout theseveral views. The drawings, which are not necessarily to scale, depictillustrative embodiments and are not intended to limit the scope of theinvention.

FIG. 1 is a schematic view of a balloon angioplasty catheter. Thecatheter 10 includes a proximal hub assembly 12 and a distal balloon 14(which may include cutting elements as further illustrated below) withan elongated shaft therebetween. The catheter 10 includes a hypotube 16,a braided member 18 attached to the hypotube 16, a port joint 20, and adistal section 22. The port joint 20 may be considered either a part ofthe distal section 22 or may be a part of a midshaft 19 that runsbetween the distal section 22 and the braided member 18, or may be anintegral part of the catheter 10.

The hypotube 16 is a thin walled metallic tubular element that ispreferably made of stainless steel, though a variety of other materialsmay also be used, as desired. The hypotube 16 may include a lubriciouscoating such as a polytetrafluoroethylene coating to reduce frictionalresistance. The braided member 18 is attached to the hypotube 16 in alap joint created by passing the distal end of the hypotube 16 into thebraided member 18 by some distance, with an adhesive applied to one, theother, or both of the hypotube 16 and braided member 18. Alternatively,an adhesive may be added after placing the distal end of the hypotube 16into the braided member 18 by taking advantage of capillary actionoccurring in the small space therebetween. In other embodiments,heating, welding, or mechanical attachment may also be used to couplethe hypotube 16 to the braided member 18. An inflation lumen extendsfrom the hub 12 through the hypotube 16 and into the braided member 18,with the joint between the hypotube 16 and the braided member 18constructed to maintain the integrity of the inflation lumen.

The braided member 18 may take on a number of forms. Typically thebraided member 18 will include a lubricious inner layer and a polymericouter layer, with a braid composed of a number of filaments or strandsbraided between the inner and outer layers. A helical, double helical,coiled, or woven member may be used in place of the braid. In oneillustrative example, the braid is formed of a flat stainless steel wireof a size 0.00075 inches by 0.003 inches, and is placed between an innerpolyimide inner layer having a thickness of about 0.00075 inches and apolyether block amide (PEBAX) outer layer having a thickness of about0.0015 inches. In this illustrative example, the overall braided member18 has an inner diameter of about 0.028 inches and an outer diameter ofabout 0.0355 inches (note that these illustrative values are consideredfrom a point where two strands of the braid cross). The braid may beannealed or soft and in the illustrative example, has a pick count ofabout 55 using a 16-strand construction. Typically, the braid is woundor formed on a mandrel, slid over the inner layer, and then tightenedonto the inner layer, and the outer layer is added over the top. Thebraid may also be wound directly on the inner layer. Coextrusion of thebraid and the inner and outer layers may also be done. The above sizesand materials are merely illustrative of one particular embodiment andare not meant to be limiting.

Other embodiments may use a number of alternative braid materialsincluding, for example, tungsten, Ni—Ti alloys, hardened steel, liquidcrystal polymers and other metallic or synthetic materials.Additionally, the pick count and number of strands used may be variedwidely depending on the desired final characteristics. It should benoted that there is a trade off where, as pick count increases,pushability also increases but kink-resistance tends to decrease. Thebraided member 18 provides a transition in flexibility as well as extrakink resistance and pushability from the distal end of the hypotube 16to more distal portions of the catheter.

Distal of the braided member 18 is a port joint 20 in the midshaft 19.The port joint 20 allows a guidewire to be inserted and carried withinthe catheter 10 distally from the port joint 20 to at least the balloon14. In a preferred embodiment, the braided member 18 is used to form apart of the port joint 20. Distal of the port joint 20 is a distalmember 22 which includes an inflation lumen as well as a guidewirelumen. It should be noted that proximal of the port joint 20, in apreferred embodiment, the guidewire lumen is not included. There is onemore lumen distal of the port joint 20 than there is proximal of theport joint 20.

A balloon 14 is then attached to the distal member 22. In a preferredembodiment the balloon includes a number of cutting members 36, asfurther illustrated in FIG. 4. The cutting members or cutting blades caninclude any type of protrusion extending radially from at least aportion of the balloon. Radially projecting longitudinal blades aredepicted in FIG. 4. However, cutting blades can be stiffening members,elongated ridges, molded or attached polymeric ridges, polymericprotrusions and combinations thereof.

The use of the braided member 18 may allow several advantages. In oneaspect, the catheter pushability is most greatly affected by its weakestmember. Distal of the port joint 20, the catheter 10 passes over aguidewire in use, and with a guidewire through the guidewire lumen, thepushability of that section tends to be relatively good. The hypotube 16is highly pushable. Without the braided member 18, either the hypotube16 must be longer or a non-braided polymeric member can be used. Thelength of the hypotube 16, however, is somewhat limited by anatomy ofthe patient, since the hypotube 16 is ill suited to traverse the moretortuous vasculature nearer the heart. By providing the braided member18, the hypotube 16 may make up only a more proximal portion of thecatheter 10 that does not traverse particularly difficult areas of thevasculature.

FIG. 2 is a cross-sectional side view of an illustrative guidewire entryport. The braided member 18 is illustrated coupled with the distalmember 22, which includes both an outer member 22 a and an inner member22 b. The braided member 18 is shown having a triple layerconfiguration, with an outer polymeric layer 18 a that is preferably arelatively soft polymer which may include a hydrophilic coating, abraided middle layer 18 b having a metallic or non-metallicfilament/strand braid, and a lubricious inner layer 18 c. In a preferredembodiment, the distal member 22 is made of two integral pieces, anouter member which is a PEBA element and an inner tri-layer memberhaving an inner lubricious layer, a tie layer, and an outer polymerlayer. In one embodiment, the inner member 22 b is a tri-layerconstruction including an inner layer of high density polyethylene, anouter layer of PEBA and a tie-layer of a modified low densitypolyethylene. The port joint 20 allows entry of a guidewire to the innermember 22 b at the proximal end of the inner member 22 b. An optionalcore wire 24 is illustrated as crossing the port joint 20 to improvekink resistance across the port joint 20.

The core wire 24 may be provided as a full length core wire extendingfrom the proximal hub (FIG. 1), or may be attached to the proximalhypotube (FIG. 1) section by a suitable method such as brazing orwelding. The core wire 24 may attach to the hypotube 16 by crimping thehypotube 16 to surround and attach to the core wire 24 or the proximalend of the core wire 24 may extend into this distal end of the hypotube16 lumen and be affixed therein.

It should be noted that while the members 18, 22 a, 22 a are illustratedas separate pieces, in some embodiments a port joint 20 may beconstructed using a heating process (such as that discussed withreference to FIGS. 7-10A below and as shown in cross section in FIG. 3)that causes reflow of various elements such that sharp distinction ofthe several members 18, 22 a, 22 b no longer exists in an actualfabricated catheter. The port joint 20 may be constructed by anysuitable fashion, and that discussed below is only provided forillustrative purposes.

FIG. 3 is a cross-sectional view taken along like 3-3 in FIG. 2. Aguidewire lumen 30 is provided through the portion distal of the portjoint 20 (FIG. 1). The core wire 24 is seen to sit within an inflationlumen 28. The shape of the inflation lumen 28 near the port joint 20 isillustrated in accordance with the illustrative port joint discussed inFIGS. 7-11. Lumens having other shapes may also be used, as desired. Asnoted above, the illustrative port joint of FIG. 3 has been constructedso that the several elements used in making the port joint are no longerclearly discerned. The cross section includes areas of double crosshatching 18 b to indicate that a portion of the braided member 18 bstands out from what is otherwise a melted-together blend of polymers.

FIG. 4 is a cross-sectional side view of an illustrative cutting balloonshown in an inflated configuration. The cutting balloon 14 is attachedat its distal end 32 to the inner member 22 b, and at its proximal end34 to the outer member 22 a. This leaves the interior of the cuttingballoon 14 in fluid communication with a generally annular inflationlumen 40 defined between the outer member 22 a and the inner member 22b. The balloon 14 may be attached using heat welding processes,adhesives, or a heat shrink wrapping, for example. Two marker bands 38are included on the inner member 22 b to aid in visualizing the locationof the balloon 14 in the vasculature. The balloon 14 may be made fromtypical angioplasty balloon materials including, for example, polymersor blends of polymers such as polyethylene terephthalate (PET),polyetherimid (PEI), and/or polyethylene (PE).

On the surface of the balloon 14 are a number of cutting elements 36.The cutting elements 36 may be disposed in any configuration including,for example, two, four or six equally spaced cutting elements 36. Thecutting elements 36 may be blades or other structures configured forcutting into plaque or tissue such as a lesion. While the cuttingelements 36 may be made of metal, the exact composition of the cuttingelements 36 may vary and may include, for example, hard, flexibleplastics. In use, when the balloon 14 is inflated, the cutting elements36 create cuts in surrounding tissue, lesions, or plaque. These cuts arebelieved to create scoring that improves removal of a blockage and alsoreduces the occurrence of re-stenosis.

The inner member 22 b extends through the balloon 14 to the distal tipof the catheter. A guidewire lumen 42 through the inner member 22 ballows the balloon 14 and catheter to be advanced over a guidewire whichpasses through guidewire lumen 42 of the inner member 22 b.

FIG. 5 is a cross-sectional view taken along line 5-5 in FIG. 4. Asshown in FIG. 5, the outer member 22 a surrounds the inner member 22 bsuch that a generally annular inflation lumen 40 is definedtherebetween. This inflation lumen 40 is in fluid communication with theballoon as well as the proximal end of the catheter, and is used forallowing an inflation fluid to be passed into the catheter, throughseveral proximal elements, through the annular lumen, and into a balloonat the distal end. The inner member 22 b defines a guidewire lumen 42.

FIG. 6 is a cross-sectional view taken along line 6-6 in FIG. 4. It canbe seen that the cutting elements 36 extend out from the outer surfaceof the balloon 14. It should be noted that the several Figures are notnecessarily to scale. The guidewire lumen 42 is separated from theinterior of the balloon by the inner member 22 b.

FIGS. 7-10 are provided to show an illustrative “slit and flare” methodfor forming a port joint in a catheter such as the port joint 20illustrated in FIG. 2. This illustrative method is provided merely toallow one skilled in the art to practice the invention. However, othermethods for producing a port joint may also be used. Instead of a slitand flare method, for example, a proximal member may be crimped tocreate a guidewire entry location, and a guidewire receiving tubularelement provided distal of the crimp.

FIG. 7 is a top view of an illustrative slit and flared midshaft member.The midshaft member 60 is preferably a multilayer shaft with a braid orother support structure. In FIG. 7, the braid is not shown to aid indepicting the joint. As can be seen, one end of the midshaft member 60has been slit and flared to create a flared portion 62 and a tab 64. Themidshaft member 60 is used as noted below with respect to FIG. 10. Amandrel (not shown) having a crescent shaped end is loaded through themidshaft member 60 with the crescent end passing out through the slitand flared end of the midshaft member 60.

FIG. 8 is a side view showing a step of forming an illustrative portjoint. An inner member 66 has been skived at one end at an angle ofabout 60 degrees. For the illustrative port joint, the inner member is atri-layer design having a lubricious inner polymer layer (preferably ahigh density polyethylene), a tie layer, and a poly-ether block amide(PEBA) outer layer, where the tie layer is used in the conventionalmanner to allow the lubricious inner layer to adhere to the PEBA outerlayer. Other lubricious materials, tie layers, and outer layers may beused as desired. The skive 68 is shaped to enable ready fabrication of aguidewire entry port, with the guidewire entering through the skive 68.The inner member 66 is shown with an inner mandrel 70 extending throughthe skive 68. The inner member 66 is loaded through an outer member 72until the skive 68 passes out of the outer member 72.

A crescent mandrel 74 is illustrated as passing into the outer member72. The crescent mandrel 74 includes a curved “bed” which allows it topass between the inner member 66 and the outer member 72, with one sideof the curved area of the crescent mandrel 74 generally matching theinner wall of the outer member 72. The other side of the curved area isshaped to match the outer wall of the inner member 66. The skive 68 isaligned to open facing away from the crescent mandrel 74.

FIG. 8A is a cross sectional view taken along line A-A in FIG. 8. As canbe seen from FIG. 8A, the curved portion of the crescent mandrel 74 isshaped to slide in between the inner member 66 and the outer member 72.There is some amount of extra space allowed, which is used to receivethe tab 64 (FIG. 7) of the midshaft member 60 (FIG. 7), as furtherillustrated below in FIGS. 10-10A. The other mandrel 70 is illustratedin place for maintaining the shape and position of the inner member 66during subsequent placement, shrink wrapping, and laser weldingprocesses.

FIG. 9 is a side view showing another step in forming an illustrativeport joint. With the crescent mandrel 74 placed as illustrated in FIG.8, the midshaft member 60 is slid toward the distal inner member 66 anddistal outer member 72. The tab 64 is placed between the distal innermember 66 and the crescent mandrel 74. For the illustrative method, thetab is only about 1.25 millimeters long, while the crescent mandrel 74extends about 8 millimeters into the distal outer member 72, so thecrescent mandrel 74 prevents the tab 64 from touching the distal outermember 72. The short side of the distal inner member 66 extends about 1millimeter past the end of the distal outer member.

FIG. 10 is a side view showing yet another step in forming anillustrative port joint. After the configuration of FIG. 9 is achieved,with the tab 64 (not shown) properly placed as explained, the midshaftmember 60 is slid over the crescent mandrel 74 until the slits thatdefine the tab 64 (not shown) bottom out against the outer member 72.The flared portion 62 is placed to partially surround the distal outermember 72.

FIG. 10A is a cross-sectional view taken along line A-A in FIG. 10. Asillustrated, the crescent mandrel 74 sits between the outer member 72and the tab 64 of the midshaft member 60. The tab 64 sits against theinner member 66, while the inner member sits against the outer member 72on its other side.

Once in the configuration of FIGS. 10-10A, a heat shrink member isplaced over the port joint to secure the various elements in place. Thena laser heating process is used to cause reflow and fusion between theseveral pieces. The heat shrink member and mandrels are then removed,and the finished port joint subassembly is used as a component of acatheter such as the catheter 10 of FIG. 1. The finished port jointsubassembly may be treated to trim any residual pieces from the heatingprocess. Also, in some methods, the port joint is skived or trimmed sothat a part of the inner member 66 is removed to create a smooth, wellcontrolled and well defined guidewire entry location.

It should be noted that in an alternative embodiment, an additionalpolymeric member may be used. For example, referring to FIG. 1, apolymeric member lacking an inner braid may be provided between the portjoint 20 and the braided member 18, with the polymeric member includedto make the fabrication of a slit and flared member for use in the portjoint 20 easier. In another embodiment, the port joint 20 may beprovided as a discrete component having a polymeric member, which mayinclude a simple single layer construction or may be more complicatedand include a braid or special tri-layer design. The polymeric membermay extend proximally and connect to the braided member 18.

Those skilled in the art will recognize that the present invention maybe manifested in a variety of forms other than the specific embodimentsdescribed herein. Accordingly, departures in form and detail may be madewithout departing from the scope and spirit of the present invention asdescribed in the appended claims.

What is claimed is:
 1. A rapid exchange catheter comprising: anelongated shaft having a proximal end and a distal end, the elongatedshaft including: a hypotube having a proximal end and a distal end; amidshaft portion having a proximal end and a distal end, the midshaftportion being attached near its proximal end to a location near thedistal end of the hypotube, the midshaft portion including a coiledmember; and a distal portion including an inner tubular member and anouter tubular member surrounding the inner tubular member, a shortguidewire lumen being defined by the inner tubular member and aninflation lumen being defined between the inner tubular member and theouter tubular member, the distal portion being attached to the midshaftportion and extending distally therefrom; wherein the midshaft portionincludes a flared portion and a tab prior to being attached to thedistal portion such that when the midshaft portion and the distalportion are attached at a port joint the inner tubular member extendsalong an exterior surface of the tab to provide a proximal guidewireport; a balloon disposed near the distal end of the elongated shaft; anda core wire attached to the hypotube and extending distally of thedistal end of the hypotube and across the location at which the proximalend of the midshaft portion is attached to the distal end of thehypotube.
 2. The rapid exchange catheter of claim 1, wherein the corewire extends distally beyond the proximal guidewire port.
 3. The rapidexchange catheter of claim 1, wherein the core wire is tapered.
 4. Therapid exchange catheter of claim 1, wherein the midshaft portionincludes a polymeric outer layer surrounding the coiled member.
 5. Therapid exchange catheter of claim 1, further comprising a polymerictubular member extending between the port joint and a distal end of thecoiled member.
 6. The rapid exchange catheter of claim 1, wherein thehypotube includes a crimp to attach the core wire to the hypotube. 7.The rapid exchange catheter of claim 1, wherein a proximal end of theinner tubular member is skived at an angle.
 8. The rapid exchangecatheter of claim 7, wherein the angle is about 60°.
 9. The rapidexchange catheter of claim 1, wherein the inner tubular member extendsthrough the balloon to a distal tip.
 10. A rapid exchange cathetercomprising: an elongated shaft having a proximal end and a distal end,the elongated shaft including: a hypotube having a proximal end and adistal end; a midshaft portion having a proximal end and a distal end,the midshaft portion being attached near its proximal end to a locationnear the distal end of the hypotube, the midshaft portion including acoiled member; and a distal portion including an inner tubular memberand an outer tubular member surrounding the inner tubular member, ashort guidewire lumen being defined by the inner tubular member and aninflation lumen being defined between the inner tubular member and theouter tubular member, the distal portion being attached to the midshaftportion and extending distally therefrom; wherein the midshaft portionincludes polymeric member extending distal of the coiled member, thepolymeric member including a flared portion and a tab prior to beingattached to the distal portion such that when the midshaft portion andthe distal portion are attached at a port joint the inner tubular memberextends along an exterior surface of the tab to provide a proximalguidewire port; a balloon disposed near the distal end of the elongatedshaft; and a core wire attached to the hypotube and extending distallyof the distal end of the hypotube and across the location at which theproximal end of the midshaft portion is attached to the distal end ofthe hypotube.
 11. The rapid exchange catheter of claim 10, wherein thecore wire extends distally beyond the proximal guidewire port.
 12. Therapid exchange catheter of claim 10, wherein the core wire is tapered.13. The rapid exchange catheter of claim 10, wherein the hypotubeincludes a crimp to attach the core wire to the hypotube.
 14. The rapidexchange catheter of claim 1, wherein a proximal end of the innertubular member is skived at an angle.
 15. The rapid exchange catheter ofclaim 14, wherein the angle is about 60°.
 16. The rapid exchangecatheter of claim 10, wherein the inner tubular member extends throughthe balloon to a distal tip.